A disk drive system typically has one or more magnetic recording media (a.k.a., disks) and control mechanisms for storing data within approximately circular tracks on the disk. The magnetic recording media is composed of a substrate and one or more layers deposited on the substrate. A substrate may be produced from a blank sheet of, for example, metal-based material such as aluminum or aluminum magnesium. The sheet may be punched to generate a disk-shaped substrate having an inner diameter (ID) and an outer diameter (OD). The disk-shaped substrate may be further processed (e.g., polished, textured, layer deposition, etc.) to produce the magnetic recording disk.
Advancing the art of magnetic hard disk drives involves increasing the recording density of a disk drive system. Recording density is a measure of the amount of data that may be stored in a given area of disk. One method for increasing recording densities is to pattern the surface of the disk to form discrete tracks, referred to as discrete track recording (DTR). The recessed zones separate the raised zones to inhibit or prevent the unintended storage of data in the raised zones.
One method of producing DTR magnetic recording media includes using a press to imprint embossable films residing on one or both sides of the recording disk substrate. The press utilizes a die for each side of the media to be imprinted. The die may include an embossing foil, or stamper, that is pressed into the embossable film of the media to form the imprinted pattern in the film. The pattern is subsequently transferred to the substrate and/or one or more layers residing above the substrate.
A press for magnetic recording disks may utilize a mandrel, or shaft, having a diameter that is sized to engage the ID of the disk. The dies have a cylindrical opening sized to receive the mandrel. The embossing foil is disposed around the mandrel and, thus, has an annular, or disk, shape with an inner diameter (i.e., a hole, or cavity, at their centers). Alignment of the embossing foil to the recording media is very important to achieve proper function in the recording media and such alignment is very challenging, particularly for double-side recording media where alignment of a mandrel holding a disk to an embossing foil on a first (bottom) die may induce alignment error relative to another embossing foil on a second (top) die. A press which maintains proper centering of a disk to both the top and bottom die as the press is operated from an open to a closed position is therefore advantageous.
Throughput of presses for magnetic recording disks may also be limited by the need to accurately imprint sub-micron (e.g., nanometer) features with high precision. For example, it is difficult to drive a press rapidly from an open state, where the dies are displaced far enough from one another that a disk may be loaded or unloaded from the press, to closed state, where nanometer features are formed (all the while maintaining the centering of the disk). A press which improves the rate at which it transitions from the open to closed state is therefore also advantageous.
A single-sided press for magnetic recording disks may also have an embossing foil affixed to a die. It can be challenging to prevent a foil-to-die coupling mechanism present on a first die of a double-sided press from adversely impacting the coupling mechanism on an opposing die as the press is closed. Furthermore, both single and double-side press systems are susceptible to the embossing foil bowing uncontrollably from center to edge (e.g., under the foil's own weight) while the press is in an open state, or buckling while the press is in a closed state (e.g., from radial expansion of the foil), either of which may produce a waviness in the imprinted features. A foil-to-die coupling mechanism which can overcome these difficulties is advantageous.